1. Field of Invention
The present invention relates to a flat panel display (FPD), a light emitting module for use in the FPD, and an integrated circuit for use in the light emitting module; particularly, it relates to a FPD, a light emitting module for use in the FPD, and an integrated circuit for use in the light emitting module with simplified wiring.
2. Description of Related Art
FIG. 1 shows a conventional FPD, which includes a display module 10 for displaying an image; a power management circuit 20, which converts an input voltage Vin to an output voltage Vout according to a feedback signal; and multiple light emitting device strings 32 for illuminating the display module 10. Each light emitting device string 32 includes multiple light emitting devices connected in series. One end of each light emitting device string 32 is coupled to the output voltage Vout for receiving power; the other end thereof is coupled to the power management circuit 20 for adjusting current through the light emitting device string 32, and generating the feedback signal accordingly. In some applications, the brightness of the light emitting device strings 32 is adjustable; in such case, the power management circuit 20 receives a dimming signal Dim, and adjusts the brightness of the light emitting device strings 32 according to the dimming signal Dim.
The power management circuit 20 may be as shown in FIG. 2. As shown in the figure, the power management circuit includes a voltage converter circuit 21, an error amplifier circuit 23, a minimum voltage selection circuit 25, and multiple current sources 27. The voltage converter circuit 21 receives a feedback control signal Vc from the error amplifier circuit 23, and the voltage converter circuit 21 converts the input voltage Vin to the output voltage Vout according to the feedback control signal Vc. The error amplifier circuit 23 receives a minimum voltage Vmin, and compares the minimum voltage Vmin with a reference voltage Vref1 to output the feedback signal Vc. The minimum voltage selection circuit 25 receives N current sense signals CS1, CS2, CS3, . . . , CSN, and generates the minimum voltage Vmin according to the N current sense signals CS1, CS2, CS3, . . . , CSN. The multiple current sources 27 are coupled to a first to an Nth different light emitting device strings 32, i.e., L1, L2, L3, . . . , LN, respectively, to control current through respective light emitting device strings 32 (L1, L2, L3, . . . , LN).
The power management circuit 20 may also be as shown in FIG. 3, wherein the transistors and resistors of the current sources 27 are provided outside the integrated circuit chip 23, but the function and operation thereof are the same as the circuit shown in FIG. 2. In this arrangement, the chip 23 needs three pins for each current source 27, that is, voltage signal pins LED1, LED2, . . . , LEDn, control signal pins Gate1, Gate2, . . . , Gaten, and current sense pins Sense1, Sense2, . . . , Sensen.
In the aforementioned conventional FPDs, regardless whether the current sources 27 are provided inside or partially outside the chip, each light emitting device string 32 needs to be coupled to the power management circuit 20 individually. The larger the size of the FPD is, the more the light emitting device strings 32 are needed in number, and so are the number and length of wires required for connection. This means more complicate wiring and more space in need. For example, as shown in FIG. 1, N light emitting device strings 32 require N+1 wires. Besides, if the light emitting devices are connected in series in one light emitting device string 32 by a larger number, a higher operation voltage is required, which leads to higher manufacturing cost and safety concern. Furthermore, when the number of the light emitting device string 32 or the number of the light emitting devices in one light emitting device string 32 changes, the power management circuit 20 and the wiring need to be modified correspondingly. These changes and modifications lead to a higher manufacturing cost.
In view of the foregoing, the present invention provides a FPD, a light emitting module for use in the FPD, and an integrated circuit for use in the light emitting module with a simplified wiring, as solutions to the aforementioned problems.